Bug 10335: display translated forms of headings in UNIMARC authorities correctly

To reproduce and test:

To reproduce:
1) Create an authority record with main heading (100) in Latin script
   (e.g. Oppenheimer, Aharon -- subfields $a and $b) and parallel form
   (700) in Hebrew (אופנהיימר, אהרן -- subfields $a and $b).
    Mark it correctly in $8 with freheb (or engheb if you like);
2) Reindex and search;
3) You will see:

Oppenheimer Aharon
freheb: אופנהיימר

Whereas you would rather like to see (mind language and lack of $b above):

Oppenheimer, Aharon
Hebrew: אופנהיימר, אהרן

The patch corrects the issue and should not harm those who (improperly)
put only one triple in $8

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work as described. No koha-qa errors.
Same result on OPAC and STAFF

Turns out that test plan is wrong,
you neet to fill tag 200ab, not 100ab, for main heading.
I filled 100a with some example data from UNIMARC auth manual.

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Took me a bit to figure it out, works according to test plan.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>